U.S. Pat. No. 4,582,876 describes blends of copolyesters and styrene-butadiene-maleic anhydride copolymers that have high impact at low temperatures. That disclosure did not make the present discovery obvious, however, since that styrenic polymer had rubbery inclusions that were believed to cause the high impact strengths of the blends. The morphology of the styrene-butadiene of the present invention is not similar to that disclosed in the '876 patent and was not expected to result in high impact strengths when blended with polyesters.
Also of interest are U.S. Pat. Nos. 4,117,034; 3,644,574; 4,352,907; 3,564,077; 4,096,202; 3,919,353; German Patent No. 3,332,325, and Japanese Patent No. 5371155.